ROBUST DIGITAL TRACKING WITH PERTURBATION ESTIMATION VIA THE EULER OPERATOR

A model reference control (MRC) method is presented for linear, time-i nvariant systems with unknown dynamics. The class of systems investiga ted can be described by x(t) = (A + Delta A) x(t) + (B + Delta B) u(t) + d(t) where Delta A, Delta B and d(t) are unknown dynamics and unexp ected disturbances, respectively. The design method is described in th e discrete time form using the Euler operator, which approaches the La place operator as the sampling interval, T, approaches zero. The contr ol is constructed, based on the estimation of system perturbations usi ng time delay control (TDC), under the following two assumptions: (1) the dynamics stemming from the perturbations are considerably slower t han the discretization frequency, 1/T; and (2) the control has access to all the plant states. The controller is tested through simulation a nd experiment. The theoretical and experimental results indicate that the proposed method has potential applications for controlling servo-m echanisms subjected to unknown and unexpected disturbances.